ABSTRACT This Phase I STTR is designed to evaluate the feasibility of using the OsteoFab technology platform for joint arthroplasty (ArthroFab?) devices, specifically targeting replacement of the small carpal bones in the wrist and hemiarthroplasty. OsteoFab technology is the combination of Oxford Performance Materials' proprietary formulation of polyetherketoneketone (OXPEKK polymer) and additive manufacturing (3D printing). This STTR builds on an existing collaboration between Dr. Joseph Crisco and his team in the Department of Orthopaedics at the Warren Alpert Medical School of Brown University/Rhode Island Hospital, and Oxford Performance Materials, Inc. (OPM), a small business in South Windsor, CT that is a world leader in bone replacements using 3D additive manufacturing. OPM currently markets FDA-cleared patient-specific devices for cranial and facial bone reconstruction (OsteoFab) and holds a clearance for a vertebral body replacement system (SpineFab) worldwide. However, the performance of OPM's OsteoFab devices has not yet been investigated in synovial joints, nor in direct articulation with cartilage. In this project we will assess the feasibility of using the OsteoFab manufacturing process to fabricate small articulating bone replacements. We propose two independent specific aims. In our first Aim we will use an established lunate resection model in the rabbit forepaw to evaluate cartilage health, local inflammation, and bony changes after 12 weeks of OsteoFab arthroplasty. The ArthoFab?-Lunate device will be fabricated and finished by OPM, based on an average lunate bone model generated using our well-established computational and morphological modeling algorithms. The average lunate will be 3D printed in laser-sintered OXPEKK polymer and the articular surfaces will be polished, with features for soft tissue attachment. Six (6) animals will receive ArthoFab?-Lunate devices and six will undergo lunate excision alone. In our second Aim, we will assess in vitro cartilage wear response to cyclic loading in a hemiarthroplasty model via pendulum testing (136,800 cycles). 3D models of the rabbit knee will be used to fabricate articulating ArthoFab?-Tibia models. Explanted fresh rabbit distal femur condyles will be flexed and extended against the ArthoFab? tibial devices with a compressive load of 1 kg at 1 Hz for 38 hours. Cartilage damage will be determined with histopathology after 14 (n=9) and 38 (n=9) hours of cyclic testing. Changes in joint mechanics will be assessed by coefficient of friction (COF) measurements at 0, 2, 14, 26 and 38 hours of testing. The work outlined in this Phase I STTR will provide critical feasibility data for the development of a research strategy for commercialization of ArthroFab? as a highly innovative, additively manufactured patient-specific device for small bone arthroplasty and hemiarthroplasty, with the potential for a significant impact on the surgical treatment of osteoarthritis and en bloc tumor resections.